This invention relates generally to printed circuit board assemblies, and, more particularly, to surface mount printed circuit board assemblies including standoffs.
With the recent proliferation of integrated circuit devices in a wide range of products, locating the integrated circuit devices with respect to an applicable printed circuit board has become a challenge. For space saving reasons, printed circuit boards are sometimes stacked upon one another. As the integrated circuit devices are connected to the printed circuit boards, the boards tend to flex, which can damage the conductive traces in a printed circuit board, damage electrical components on another printed circuit board, and produce undesirable electrical losses in the system. In some cases these effects can be alleviated by using known standoffs to add support to the printed circuit board assembly. Typically, the standoffs are substantially cylindrical and are attached to the printed circuit boards with a fastening member, such as resilient legs, springs, or screws via through-holes in a printed circuit board. Conventional standoffs, however, require some dexterity to properly install and therefore require hand installation, which increases costs of assembly and leads to some variation in product quality and reliability.
To simplify assembly and save further space, surface mount components are becoming increasingly popular. Surface mount components are soldered directly to the printed circuit board, and component leads and through-holes in the board may therefore be avoided. To avoid increased expense and difficulty of conventional standoffs in surface mount applications, surface mount components themselves, such as resistors, have been used solely to support the printed circuit boards and prevent excessive flexing of the board during connection of the integrated circuit devices. However, using non-functional components such as resistors for support purposes can significantly affect the cost of the printed circuit board assembly and increase the weight of the final assembly. Further, while plastic inserts have been used in lieu of nonfunctional surface mount components to support printed circuit board assemblies, they typically require through-holes in the board, are difficult to work with, and are inefficient from a manufacturing perspective.
In one aspect, a standoff for a printed circuit board assembly is provided. The standoff comprises at least one surface configured for surface mounting to a printed circuit board.
In another aspect, a standoff for a printed circuit board including at least a first conductive trace pad and a second conductive trace pad for establishing a circuit to determine the presence of a number of standoffs if provided. The standoff comprises at least one surface having a dimension at least equal to a distance between the first and second conductive trace pads, said standoff at least partially conductive between said first and second trace pads.
In another aspect, a printed circuit board assembly is provided. The assembly comprises a first printed circuit board, a second printed circuit board, and at least one standoff in contact with each of said first and second printed circuit boards, said standoff surface mounted to at least one of said first and second printed circuit boards.
In another aspect, a method for determining the presence of a number of standoffs in a printed circuit board assembly is provided. The printed circuit board assembly includes at least one printed circuit board including conductive circuit traces having at least one pair of contact pads where each of the standoffs are to be located, and the conductive traces having at least a first termination and a second termination. The method comprises mounting the standoffs to the printed circuit board in electrical contact with respective pairs of contact pads, applying an electrical signal to said first trace termination, and detecting the presence or absence of the electrical signal at said second trace termination.